Coupled Algebraic Multigrid for Free Surface Flow Simulations

Abstract

An accurate, efficient algorithm for solving free surface flows with ANSYS CFX is described. Accuracy is achieved using a compressive advection discretization which maintains a sharp free surface interface representation without relying on a small timestep. Efficiency is obtained using a solution algorithm which implicitly couples velocity, pressure, and volume fractions in the same matrix, and solves these equations using algebraic multigrid. This coupled strategy overcomes difficulties encountered with segregated volume fraction algorithms, where heavy underrelaxation and long solution times are required. The resulting solution algorithm is scalable, leading to solution times which increase linearly with mesh size.